This invention relates generally to an injection molded preform made of thermoplastic material and adapted to be formed into a container during a blow molding operation.
More specifically, the invention relates to a preform for use in blow molding a relatively large and generally cylindrical bottle (e.g., a five gallon bottle) for holding purified drinking water or the like. Bottles of this type usually include a generally cylindrical body, a generally frustoconical top breast at the upper end of the body, and a tubular filling and dispensing neck projecting upwardly from the central portion of the breast. In order to enable the bottle to be used with standard filling equipment, the inner diameter of the neck is approximately 1-5/8" and is small in comparison to the inner diameter (e.g., about 10") of the generally cylindrical body of the bottle.
While the preform may be made of various thermoplastic materials, the preferred material is polyethylene terephthalate (PET). Such material is recognized as being superior in many respects to materials such as polycarbonate and polyvinylchloride for use in water bottles and the like.
Blow molding of injection molded PET preforms is a widely used process for producing relatively small (e.g., two liter) bottles. Also, the assignee of the present invention has used such a process to make relatively large (e.g., 20 liter) spherical PET containers for use with draft beer or the like, such containers being known by the trade designator BEER SPHERE.
Large (e.g., five gallon) and generally cylindrical water bottles for use with standard filling equipment and standard dispensers have not been previously produced on a commercial basis by blow molding an injection molded PET preform. The difficulty in producing such a bottle resides in part in keeping the diameter of the filling and dispensing neck small in relation to the diameter of the generally cylindrical body while still imparting adequate strength to the container. A particularly vulnerable area of the container is its frustoconical top breast since the breast must support considerable weight when filled bottles are stacked on top of one another during shipment.